1. Field of the Invention
The present invention is related to the field of conveying technology and concerns a method and a device for transforming a conveying stream of flat articles, such as for establishing from a conveying stream, in which all articles have the same orientation, a conveying stream with alternating article groups, in which the articles are differently oriented.
2. Description of the Related Art
For conveying flat articles, such as printed products (e.g., newspapers, periodicals, etc.), in many cases grippers are used. The grippers move one behind the other and each one holds an article in an edge zone. Usually, all held articles are oriented in substantially the same way. In such a conveying stream periodicals are, for example, held gripped from above in the zone of their spine edge and are conveyed such that all front sides are facing downstream.
Printed products, such as the named periodicals, are, for example, conveyed to a stacking shaft in which they are deposited in a stack. If this stack is to be a cross stack, which is a stack in which the articles form alternating groups rotated by 180xc2x0 relative to one another (spine edges of the periodicals positioned partially on one and partially on the other side of the stack), the stacking shaft and the stack being produced are rotated after the depositing of each group of printed products. This is described in the publication DE-2842117 (or U.S. Pat. No. 4,214,743). For the same purpose, it is also known, as described in the publication DE-19530499 (Gorny), to split the conveying stream into two partial streams prior to deposition of the printed products in the stacking shaft and to convey the two partial streams to the stacking shaft in a different manner or direction. In this way, the printed products conveyed in one part stream are rotated by 180xc2x0 relative to the printed products conveyed in the other part stream. It is further known, to rotate printed products groupwise in the conveying stream and to stack the so-transformed stream in this manner to create cross stacks without the need of further measures. A device for transforming a conveying stream in this manner is described, for example, in the publication EP-0854105. The described transformation concerns a conveying stream, in which the products are conveyed held gripped individually, and the transformation is implemented by temporarily taking over the products by grippers of an auxiliary system.
The devices for implementing the known methods using stack rotation are relatively simple, providing that stopping the article supply for every stack rotation is acceptable. If, however, the performance capacity has to be high or the cycle time has to be as short as possible, either a switch point has to be provided for splitting the supply stream such that the products can be supplied to two stacking shafts or else the articles supplied during stack rotation have to be intermediately stacked. Both measures render the devices significantly more elaborate. The methods mentioned above using stream splitting for different ways of supply of the part streams, as well as the methods using stream transformation, can be implemented with more simple stacking devices and higher performance capacities. However, for splitting or transforming the stream more elaborate devices and control systems are needed.
The present invention is directed toward a method and device for transforming a conveying-in stream, in which flat articles are conveyed held gripped individually, into a conveying-out stream, in which the articles form groups that are orientated differently. The method according to the invention is to be significantly simpler than known conveying stream transformations serving similar purposes. Nonetheless, the stream transformation is to be capable of being implemented for article groups of varying sizes. The method in accordance with the invention is to be able to be implemented using a very simple device and a simple control system.
In most cases the method according to the invention will produce from a conveying-in stream, in which the flat articles are oriented in substantially the same way, a conveying-away stream, in which the articles of successive groups are alternately differently oriented such that, when they are conveyed to a stacking shaft, the successive groups of articles are stacked in a cross stack without further measures needed. Obviously, the method in accordance with the invention can also used for transforming a conveying-in stream, in which the articles have differing orientations, into a conveying-away stream, in which the articles have all the same orientation or have again differing orientations.
In accordance with the inventive method, the conveying-in track, along which the articles are conveyed individually held, intersects twice with a conveying-away track, along which the articles are conveyed away in a transformed stream, and of handing over conveyed-in groups of articles from the conveying-in track to the conveying-away track alternately at the first and at the second track intersection. The handing-over is preferably a simple depositing of the articles conveyed, each held by a gripper, along the conveying-in track, onto a conveying substrate, such as a conveyor belt, moving along the conveying-away track.
The angle of intersection between the conveying-in track and the conveying-away track for both track intersections is, for example, 90xc2x0, but may also be greater or smaller than 90xc2x0. In both handing-overs, the printed products are reoriented in dependence upon the intersection angle, for example, by 90xc2x0 (e.g., transformation of transverse conveying to longitudinal conveying for rectangular, flat articles). Because the conveying-in track meets the conveying-away track from opposite sides in the two track intersections, there is, in addition to the above mentioned re-orientation, a rotation by 180xc2x0 for articles handed over at the one intersection relative to articles handed over at the other intersection. Therefore, in a stream transformed with the method according to the invention, articles of every second group are rotated by 180xc2x0 relative to articles of the respectively first groups.
Advantageously, the articles are conveyed in the conveying-in stream transverse to their plane extent. The articles are, for example, held gripped at a top edge and are substantially freely suspended, wherein the distances between the products are smaller than their plane extent. Advantageously also, the articles conveyed-in in this manner are deposited onto the conveying substrate of the conveying-away track overlapping one another, so that the transformed conveying-away stream is an imbricated stream comprising gaps at least after every second group of articles.
In accordance with the inventive device, a conveying-in means defines a conveying-in track and has grippers arranged one behind the other and movable along the conveying-in track in a conveying-in direction. The device further comprises a conveying-away means defining a conveying-away track, which at least in a transformation zone comprises a conveying substrate extending along the conveying-away track and moving in a conveying-away direction. In the transformation zone, the conveying-in track and conveying-away track intersect twice. Furthermore, the device comprises control means in the transformation zone for selectively opening the grippers for a groupwise handing-over of articles at the first and at the second track intersection.
In further accordance with the present invention, the grippers of the conveying-in means are independent of one another such that the distances between these grippers are variable and the grippers can be stopped and buffered immediately upstream of the track intersections.